Etching

Which solution is commonly used for wet etching of silicon nitride?

  1. ADeionized water
  2. BHot phosphoric acid
  3. CAmmonia water
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Answer: B. Hot phosphoric acid

Silicon nitride can be etched with phosphoric acid heated to about 150 °C, with high selectivity to oxide. It is used, for example, to remove nitride masks after LOCOS or STI formation. Oxide is etched with hydrofluoric-acid-based solutions.

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More Etching questions

  1. During plasma etching, what is the phenomenon called in which conductors acting as antennas, such as long wires, collect charge and damage the gate oxide they connect to?
  2. Which is a characteristic of wet etching of silicon with potassium hydroxide (KOH) solution?
  3. Which is a characteristic of inductively coupled plasma (ICP) etching equipment?
  4. Which metric indicates how small the variation in etch rate is across the wafer?
  5. After the etch endpoint is detected, what is it called to continue etching for a set time to ensure the film is removed across the whole wafer?